gnu: i7z: Fix building with GCC >= 10.

* gnu/packages/hardware.scm (i7z)[source]: Add patch.
* gnu/packages/patches/i7z-gcc-10.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -1255,6 +1255,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/hurd-cross.patch				\
   %D%/packages/patches/hurd-xattr.patch				\
   %D%/packages/patches/hydra-disable-darcs-test.patch		\
+  %D%/packages/patches/i7z-gcc-10.patch				\
   %D%/packages/patches/icecat-makeicecat.patch			\
   %D%/packages/patches/icecat-avoid-bundled-libraries.patch	\
   %D%/packages/patches/icecat-use-older-reveal-hidden-html.patch	\

gnu/packages/hardware.scm

@@ -25,6 +25,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu packages hardware)
+  #:use-module (gnu packages)
   #:use-module (gnu packages admin)
   #:use-module (gnu packages autotools)
   #:use-module (gnu packages bash)
@@ -330,6 +331,8 @@ whether the hardware works with a fully free operating system or not.")
          (file-name (git-file-name name version))
          (sha256
           (base32 "0jxm63a8y1mfl1sa4mzzfs3bgnym6achj1yc0jglmp05xal16lm1"))
+         (patches
+          (search-patches "i7z-gcc-10.patch"))
          (modules '((guix build utils)))
          (snippet
           '(begin

gnu/packages/patches/i7z-gcc-10.patch

@@ -0,0 +1,23 @@
+From: Tobias Geerinckx-Rice <me@tobias.gr>
+Date: Sat, 11 Dec 2021 19:22:49 +0100
+Subject: [PATCH] gnu: i7z: Build with GCC 10.
+
+Patch from Debian, modified to apply to our i7z sources in src/.
+
+Author: Andreas Beckmann <anbe@debian.org>
+Description: fix FTBFS with gcc-10
+ gcc-10 defaults to -fno-common
+ see https://gcc.gnu.org/gcc-10/porting_to.html
+Bug-Debian: https://bugs.debian.org/957351
+
+--- a/src/i7z_Dual_Socket.c
++++ b/src/i7z_Dual_Socket.c
+@@ -37,7 +37,7 @@ float Read_Voltage_CPU(int cpu_num);
+ extern struct program_options prog_options;
+ FILE *fp_log_file;
+ 
+-struct timespec global_ts;
++extern struct timespec global_ts;
+ extern FILE *fp_log_file_freq_1, *fp_log_file_freq_2;
+ 
+ extern char* CPU_FREQUENCY_LOGGING_FILE_single;